The combination of two technologies- horizontal drilling and hydraulic fracturing- made it possible to produce shale oil reservoirs economically.Although the massive stimulation treatment is the primary solution to recover efficient amount of oil from shale oil reservoirs, the recovery factors of these reservoirs are expected to be around 5-10%.The enormous remaining oil volumes stimulate our efforts to investigate the application of enhanced oil recovery methods in shale oil reservoirs. In unconventional reservoirs, cyclic gas injection using various gases could be an effective technique. Since it is a single-well process, well-to-well connectivity is not required. The hydraulic fracturing provides a large contact area for the injected gas to penetrate and diffuse into the low-permeability matrix swelling the volume of oil and increasing the near wellbore pressure which helps increasing the oil recovery in the production stage of this technique. Experimental and numerical studies by Gamadi et al, 2013 and 2014, and Tovar et al 2014, have shown that there is a great potential of increasing the recovery factor from shale oil formation. Since the hydraulic fracturing provides a large contact area for the injected gas to penetrate and diffuse into the low-permeability matrix, we investigated the performance of Cyclic Gas Injection on acid stimulated shale oil cores. The aim of the acid stimulation treatment was to improve the low-permeability matrix of the shale cores. The results showed that the acid treatment cores resulted in improving the porosity and permeability, this improvement led to better recovery factors comparing to unstimulated cores. In the conclusion, the combination of acid stimulation treatment followed by cyclic gas injection led to improving the recovery factors of the shale cores to about 50 % comparing to the unstimulated shale oil cores used in previous studies by Talal 2013 and 2014.
Presenters
Raymond Eghorieta and Gamadi Talal Texas Tech University